2007-11-26 11:12:59 · 10 answers · asked by Anonymous in Science & Mathematics ➔ Chemistry
That is determined by the number of available orbitals, with the number of atoms in each period equal to twice the number of orbitals (since each electron can have up or down spin). For example, the alkali metal/earths have two in their period since there is only one s orbital and each s orbital can hold two electrons. The transition elements are the d-orbitals, and there are five of them so there are 10 atoms in the transition period. The three p-orbitals correspond to the six right-hand columns of the table (with the exception of helium, which is s-only).
2007-11-26 11:23:22 · answer #1 · answered by gcnp58 7 · 1⤊ 3⤋
The period length is determined by filling the electron ring of hat period. row 1 is for the 1st ring-2 electrons
row 2 is for the 2nd ring-8 electrons
row 3 is for the 3rd ring-18 electrons
etc
2007-11-26 11:17:22 · answer #2 · answered by science teacher 7 · 1⤊ 0⤋
The number of valence electrons in the noble gas.
1st period- Helium, has 2 valence electrons
2nd period- Neon, has 8 valence electrons
4th period- Krypton, has an extra f orbital plus a 3d, making valence electrons still 8
and so on...
2007-11-26 11:16:14 · answer #3 · answered by way2hot2becool 3 · 1⤊ 0⤋
the modern periodic law states that properties of elements repeat as a function of atomic number. as soon as there is a repeat in properties, a new period starts.
2007-11-26 11:16:37 · answer #4 · answered by HansonFan 6 · 2⤊ 0⤋
http://en.wikipedia.org/wiki/Periodic_table
lots of talk about periods - happy reading.
more info than you need, but I'm sure it will be useful for the other questions your teacher has ready and waiting
2007-11-26 11:19:00 · answer #5 · answered by steven m 7 · 2⤊ 0⤋
The number of protons and neutrons
2016-05-26 01:23:40 · answer #6 · answered by darlene 3 · 0⤊ 0⤋
54
2007-11-26 11:15:24 · answer #7 · answered by Cordell W 1 · 2⤊ 5⤋
im not sure how anything is determined in the periodic table, and im in high school...think i would have known by now...oh well
2007-11-26 11:16:39 · answer #8 · answered by Anonymous · 1⤊ 4⤋
i think it is the person who made it up
2007-11-26 11:16:11 · answer #9 · answered by holeeycow 5 · 2⤊ 5⤋
do you mean row?
2007-11-26 11:15:53 · answer #10 · answered by A.C.Cobra 3 · 1⤊ 4⤋